Hi,
this site lists some info about rules to teach the kids but the software seems to be all PC.
http://www.cybersafety.us/nanny-net-for-mac.html

this site lists a link to cyberpatrol
http://www.macosarchives.com/parental_control.html
but cyber patrol doesn't have a MAC version. they do list this info tho
"Macintosh Users
For the latest information on Internet filtering for Macintosh Operating Systems you can search Apple's site at: http://guide.apple.com/ussoftware.lasso or visit the Viacomsoft site at: http://www.vicomsoft.com/vig/intergate_osx_latest.html where you may be able to find a suitable filtering solution."

going here
http://guide.apple.com/uscategories/internet.lasso
and selecting security provides a large list of software that sound like they might do what your looking for.

going here
http://www.safe-internet-access.com/filtering_solutions/filtering_safe_home.html
they have this quote
"She then installed SurfDoubler to restrict access to the Internet to certain times of the day, and to block sites that are inappropriate for youngsters."
there is also a link to "try it"

hope that helps :D

Cisco Access Point:

Cisco AP340 11.06